There are many installations--such as power plants--in which the waste heat from a steam turbine is cooled in a cooling tower, or like condenser, utilizing sea water. The sea water is typically then merely discharged back into the body of salt water from which it was withdrawn, providing a source of thermal pollution. Especially in shallow bays, this may be a significant pollution problem, and in any event it is a waste of the energy from the steam turbine.
According to the present invention, the waste steam from a steam turbine or the like is productively utilized to desalinate water--preferably sea water that is used to cool the waste steam. In this way, the amount of thermal pollution is greatly reduced, and at the same time a useful end product--fresh water--is produced.
According to the method of the present invention, fresh water is recovered from water having a substantial salt content (such as sea water) while simultaneously condensing waste steam, by practicing the following steps: a) Passing water having a substantial salt content into heat exchange relationship with waste steam, so as to condense the steam and the water having a substantial salt content; b) evaporating a portion of the heated water with substantial salt content from step (a); c) collecting the water from step (b) that does not PG,3 evaporate; d) passing the evaporated water from step (b) into heat exchange relationship with a colder fluid so that the evaporated water condenses into fresh water; and e) collecting the fresh water that condenses in step (d).
Desalination apparatus according to the present invention typically comprises the following components: A generally upright vessel having first and second chambers. A first inlet for water to be desalinated into a central portion of the first chamber. Means for distributing water introduced into the first inlet into the first chamber so that evaporation thereof is facilitated. A mist separator adjacent the top of the first chamber. A sump adjacent the bottom of the first chamber for collecting water introduced into the first inlet that does not evaporate. Means defining a passageway for water vapor from any water that evaporates in the first chamber past the mist separator and into the second chamber. Gas moving means for supplying a force moving water vapor from the first chamber into the second chamber. Condensing means in the second chamber for condensing water vapor passing from the passageway into the second chamber into product water. And, a product water sump adjacent the bottom of the second chamber for collecting product water that condenses in the second chamber. The means for distributing water introduced into the first inlet into the first chamber so that evaporation is facilitated preferably comprises a plurality of spray nozzles disposed over fill (packing) within the first chamber. A similar type structure may be provided as the condensing means, although the condensing means may also comprise a plurality of dimpled plates defining a closed circulatory path within the second chamber, or plastic membranes defining such a closed circulatory path.
When spraying and fill means are utilized as the condensing means, product water from the product water sump is circulated into heat exchange relationship with sea water to produce cooler product water. A part of the cooler product water is recovered, while another part thereof is introduced into the spraying means in the second chamber. Heated sea water used to cool the product water may then be introduced as water to be evaporated in the first chamber.
The first and second chambers may be side by side, or the second chamber may be stacked on top of the first. Preferably, a fan--mounted in the passageway between the side by side chambers, or mounted above the second chamber when they are stacked, provides the gas moving means. In lieu of a fan a tall natural draft will be used to the move the gas.
According to another aspect of the present invention, a combination waste steam condensing and salt water desalinating system is provided. The system comprises: a turbine having a waste steam discharge conduit; a conduit conveying cool salt water; a heat exchanger operatively connected to the cool salt water conduit and the discharge conduit, and having a warmed salt water discharge line; an evaporator connected to the warmed salt water discharge line for evaporating a portion of the water therein to produce water vapor; a condenser for condensing the water vapor from the evaporator to produce product water; and collecting means for collecting the product water produced in the condenser.
It is a primary object of the present invention to provide a method and apparatus for minimizing thermal pollution as a result of cooling waste steam from a turbine or the like, while at the same time desalinating water. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.